1. Field of Endeavor
The disclosure relates to the formulation, manufacture and use of surfacing materials that provide increased compliance and rebound in order to reduce the likelihood of injury to riders and their mounts during equestrian activities. It is anticipated that these equestrian surfacing materials will be particularly useful as a ground cover/flooring for a wide range of equestrian activities and sports, particularly as applied to horse training and race tracks, riding arenas, round pens and walkers. It is further anticipated that these equestrian surfacing materials would be suitable for use during training, thoroughbred racing, show jumping, dressage, English pleasure riding and western pleasure riding.
2. Discussion of Conventional Art
At present, there are no universal recommendations for the perfect arena surfacing or surfacing material but the general goals include providing a surface that provides cushioning to reduce concussion on horse legs and reduce the chance of injuries during a fall, that is firm enough to provide adequate traction, that does not generate much dust, that is not unduly abrasive or damaging to a horse's hooves, that maintains an acceptable combination of properties over a wide temperature range from the coldest winter mornings to the hottest summer days, provides good value and that does not require excessive maintenance. As will be appreciated, the cost of surfacing materials varies widely as a function of the various components, the local availability of some or all of the components as well as the expenses associated with manufacture, transportation and installation. The intended primary use(s) of the arena for dressage, jumping, reining or driving, for example, will also influence the selection of the surfacing material and other parameters including, for example, as traction and depth of loose material.
A variety of manufactured materials that depend less on local availability and tend to provide more uniform properties are available for installation. A range of naturally occurring or processed inorganic materials including, for example, sand, stone dust and gravel, are typically available from local or regional quarries. In many instances, these materials may be specified with regard to one or more defined characteristics including, for example, particle size, particle size distribution, particle shape and particle angularity.
Among the factors that complicate efforts to arrive at a national “target” surfacing material are the local and regional variations in the component materials, the range of temperature to which the surfacing material will be exposed, and the amount of moisture to which the material will be exposed. As noted above, however, with respect to quarried inorganic materials (for example, sand, stone dust and/or gravel), the purchaser typically has the benefit of standard industrial nomenclature that provides information relating to particle sizes and the distribution of sizes found in a particular quarried product. Particle size distribution is determined by shaking the material through a set of sieves that have increasingly smaller holes in order to separate the finer material from the progressively larger materials retained by the upper sieves.
As will also be appreciated by those skilled in the art, surfacing materials are rather dynamic and will be expected to experience some compositional and property changes with time and use. For example, arena surfacing materials are expected to accumulate manure and urine over the years use and need to be formulated and/or maintained in a way that continues to provide an acceptable combination of surfacing material properties. The surfacing materials will also be subjected to the impact of horse's hooves and, not uncommonly, cattle, maintenance vehicles and, in some instances, other vehicles as well. If the surfacing materials are not sufficiently robust, these mechanical forces can break down the surfacing material components, thereby increasing the percentage of “fines” and, consequently, increasing the likelihood of increased dust generation and/or surface compaction. In some cases, as the older material breaks down or becomes contaminated, the surfacing material may be refreshed through the addition of fresh material(s) intended to improve or renew the performance of the surfacing material.
As noted above, the primary goal in selecting surfacing materials is to provide a surface that maintains its generally loose nature while simultaneously providing a degree of stability and traction sufficient for the intended riding and/or driving activities. As known to those skilled in the art, a major component of most surfacing compositions is a mixture of inorganic sand(s), silt(s) and/or clay(s) particles. In addition to the inorganics, a range of organic bulk materials, whether original and/or added during use as in the case of horse manure) and may also include additives such as coatings, fibers and/or pieces of rubber.
A number of these products are currently available in the market and are sold under a variety of names including, for example, POLYTRACK™, TAPETA™ and CUSHION TRACK.™ However, these surfacing products tend to become both very firm at lower temperatures for example, −10° C. to 5° C., and become very soft and/or sticky at temperatures above 30° C. This temperature dependence of the properties of these surfacing materials is generally attributed to the large changes in the viscosity of the wax(es) incorporated in these formulations over this temperature range.
These changes in the viscosity and nature of the conventional manufactured surfacing products can cause the “going,” i.e., the performance of the surface as experienced by the horses and/or riders, to change dramatically over the course of a season, a day, or even simultaneously across shaded and exposed portions of a single track or arena. These changes in “going” can, in turn, result in detrimental effects on the performance, confidence and/or health of the horses. For example, at lower temperatures these surfaces will generally become too firm reduce the degree of cushioning provided to the horses legs. Conversely, at elevated temperatures these surfaces will generally exhibit reduced structural strength, increased softness and reduced traction.
It is well established in the equestrian world that surfaces which are either too firm or too soft can increase the likelihood of serious injury to the horse and/or reduce the horse's confidence and increase the likelihood of injury to a rider or jockey, particularly in those activities that involve jumping or rapid changes in direction. Further, efforts to compensate for these changes in properties of the surfacing materials over this conventional temperature range also increase the complexity and expense of maintaining such surfaces.
Sand is a common ingredient in many arena surfaces and is typically used in particle size ranges from fine sand (about 0.05 mm average diameter) to coarse sand (about 2.00 mm average diameter). Although sand can be used as the sole surfacing material, it is often combined other particle sizes or other materials to improve its stability and traction. It has been found that the loose traction resulting from thicker layers of sand, for example, a sand depth of more than about 10 cm, may result in undue stress to a horse's tendons. Further, although newly laid sand will contain air pockets that will temporarily improve its ability absorb shock and provide some rebound effect, given its mechanical strength and mineral nature, sand will tend to compact into a less suitable surface over time and/or with heavy use.
Because sand drains well and tends to dry quickly, it can produce unwanted dust unless sufficient moisture is retained in the upper portion of the surfacing material. This moisture may be provided through periodic watering, whether automatic or manual, if the rainfall is insufficient or the surface is protected. As noted above, other materials may be combined with sand to improve its ability to retain moisture including organic products including, for example, sawdust, mulch or other wood or vegetation based material, or commercial additives in the form of coatings or particles that will retain moisture and release it more slowly, thereby decreasing the need for frequent watering.
Those of skill in the art will also appreciate that all sand is not created equal. Sand used in surfacing materials should typically be cleaned (washed to remove silt and clay) and screened (passed through a series of mesh plates to separate the sand particles by size) to remove fines to obtain a sand mixture comprising medium to coarse particles of hard, sharp sand. Fines should be removed because they tend to break down further during use to form dust particles the associated issues. As used herein, “hard” or angular sand consists primarily of quarried quartz particles characterized by sharp edges and faces that stand in marked contrast to the rounded sand particles recovered from riparian sources on which the sharp edges have been reduced through abrasion.
Although “sand” is frequently one of the most widely and readily available surfacing materials, the hard, angular, washed sands that are more suitable for forming surfacing materials are among the most expensive sands. As noted above, cleaned, washed sand alone, particularly at depths of more than about 10 cm, will generally be too loose for those riding disciplines and events that incorporate sharp turns and stops, such as barrel racing and cutting. And while wetting the sand can improve the traction, the frequent and abundant watering that may be needed to maintain the sand in the appropriate moisture range may not be economically and/or technically realistic in some locations.
Combination sand-soil surfacing materials are typically more popular than pure sand for western riding events, particularly those in which improved stability is needed for speed events can be provided with a more compacted condition or, alternatively, processed or harrowed to increase the looseness of the mixture and render it more suitable for sliding stops, such as those commonly seen in roping events and cutting work. In addition to soil, other materials including, for example, wood and/or rubber particles, may be mixed with sand to overcome some of the performance shortcomings associated with sand alone. The addition of wood products will typically improve the moisture retaining capacity of the mixture, improve the traction of the mixture and add some cushioning effects. As would be expected, the addition of rubber particles including, for example, post-consumer granulated rubbers, tends to improve the cushioning properties of a sand surfacing mixture and can prolong the useful life of the surfacing material by decreasing sand-to-sand abrasion.
As noted above, wood products may be used in combination with other materials such as sand or may be used as the sole or primary footing material. Wood chips or coarse sawdust will tend to improve the cushioning and moisture-holding capacity of inorganic materials, (sand, stone dust). Wood products are, however, can vary quite widely from location to location and even from load to load from the same wood mill. In addition, wood products are not as durable as sand and will eventually breakdown and/or decompose. This degradation will typically become a problem sooner in those wood products that have a smaller initial particle size and/or are manufactured from softer woods tend to be more prone to break down into smaller particles that will eventually lead to compacted footing and/or dust generation. Some concerns have also been raised regarding the emission of volatile organic compounds (VOCs) from some of the softer woods like pine and cedar and the connection to respiratory issues. It is also recommended that walnut and cherry be excluded as sources for the wood products as they are highly toxic to horses. An advantage of predominately wood based surfacing materials is the reduced abrasiveness on horse hooves when compared with sand-based and/or stone dust-based surfacing materials. As with sand-based materials, however, in most instances a certain range of moisture needs to be maintained within the wood product to provide suitable traction. When the wood products are allowed to become either too dry or too wet the traction tends to decrease and may result in slips, falls and refusals.
As discussed above, rubber materials from, for example, recycled shoes or tires can be ground or shredded into small particles. It is particularly important that rubber from recycled tires be processed to remove any residual metal fibers (from steel-belted tires) or other foreign materials. Unlike wood products, rubber-based surfacing materials tend to decompose or break down more slowly. It is to be expected, however, that there will be some degradation simply as a result of the action of the horses' hooves in grinding the rubber products against more abrasive materials including, for example, sand and/or stone dust. The dark color of most recycled rubber may reduce glare and improve the solar heating of the surfacing materials during cold periods and speed thawing. Depending on the rubber source, rubber particles may have a specific gravity of about 1.0 or less that may cause them to float or otherwise segregate when the surfacing material is flooded, whether deliberately or during heavy rainfall events. Accordingly, provisions should be made for periodically processing the surfacing material to redistribute the rubber particles throughout the surfacing material layer.
As indicated above, stone dust is another conventional surfacing material that can provide good stability, good drainage and an attractive surface when properly maintained, typically including watering and harrowing. Although properly maintained stone dust can provide suitable footing for equestrian events, it tends to be very subject to both compaction and dust generation. If used as a primary component of a surfacing material, stone dust (also known by various regional names including, for example, blue stone, rock dust, limestone screenings, decomposed granite and white stone) should be classified (screened) to contain a narrow range of grade sizes that will be less subject to compaction. As suggested above, mixing stone dust with rubber will reduce its tendency toward compaction while preserving acceptable stability that allows for quick changes in direction and speeds during equestrian events such as jump takeoff and landing during show jumping events.
Topsoil is a very vague term and will vary widely from region to region and even from farm to farm. In general, the properties that make topsoil useful for farming make it much less suitable for use as a surfacing material. In particular, because is a widely graded material, i.e., it includes a wide range of particle sizes and frequently includes a significant percentage of fines, it is very susceptible to compaction. Further, when dry, it can be very hard and/or a significant source of dust and, when wet, can be very sticky and slippery, particularly those topsoil compositions having a large clay component. Topsoils also tend to drain more slowly than the materials discussed above and may require more time and/or treatment after a drenching before they are suitable for use. As noted above, varying combinations of topsoil and sand can provide a satisfactory combination of properties that cannot be easily attained with the individual components.
Stall waste, a combination of manure and plant or wood-based bedding materials, is sometimes used as a surfacing material, particularly in those instances where low cost is the primary decision factor. Unfortunately, stall waste tends to be largely organic and subject to rapid breakdown into small particles that increase the likelihood of compaction. In addition, concerns with regard to pests (flies in particular), dust, odor and sanitation will also be common issues for stall waste applications, particularly those that include large amounts of manure. There are also concerns associated with ammonia released by decomposing urine and manure and its potential for compromising equine respiratory systems, particularly for enclosed applications. Although the outgassing and odor issues may be reduced in outdoor applications, stall waste can still be extremely slippery when wet.
As noted above, a number of surfacing materials are commercially available and touted as addressing one or more of the concerns associated with older, more conventional surfacing materials. These second generation materials, however, have introduced other concerns, particularly with respect to the stability of the materials over wide temperature ranges.